Electrical contacts and especially those designed for carrying relatively low currents such as in the order of milliamperes require extremely small voltage drops across the contact. This means that the resistance of the contact to the flow of electricity should be as close to zero as possible. This resistivity is referred to as the contact resistance.
Because of their relatively low contact resistance, contact surfaces of precious metals such as gold, platinum, and palladium are used to a great extent in electronic applications. Not only do surfaces from these precious metal exhibit extremely low contact resistance, but also such surfaces are resistant to oxidation and thereby retain their low resistance.
However, in view of the expense of such precious metals, attempts and suggestions of eliminating or at least reducing the amount of such materials have been made. Such prior suggestions have not been entirely satisfactory.
The problem becomes even more difficult when it is desired to provide a surface that not only exhibits relatively low electrical resistance, but also relatively high wear resistance, and resistance to oxidation.